Added PoissonGLM boolean, allows wordfishMCMC to estimate the additive GLM version of the Poisson equivalent to multionomial, where Lunn et al (2013 - BUGS Book) suggest (log) alpha should ~ dflat().
Synced tutorials
Merge branch 'dev' of https://github.com/kbenoit/quanteda into dev

Conflicts:
	tutorials/scaling/pdf/figure/minimal-unnamed-chunk-4.pdf
	tutorials/scaling/pdf/scaling.log
	tutorials/scaling/scaling-concordance.tex
	tutorials/scaling/scaling.pdf
	tutorials/scaling/scaling.synctex.gz
	tutorials/scaling/scaling.tex